#insect evolution

Why I’m glad you asked :)

Enter the common ancestor of all arthropods. They probably looked a lot like centipedes and millipedes, or even velvet worms, which are super close to arthropods. By which I mean they were long and made of segments.

Super simple! Got that? Good.

Lets go forward through evolutionary time. Now every segment has a pair of legs. Everything is very uniform and unspecialized.

Still with me?

Here’s where things get weird, the segments themselves to change size and shape, and the legs change as well. How these things change depends on the subphylum itself, but I am an insect blog so I’ll focus on them. To make a long story short:

Some of the legs migrated to the top of the segment (antennae)

Some legs in the front were used to shove food into their mouths (mandibles),

Some legs were used to sense the environment around them through touch (maxillary and labial palps).

Some of the legs on the back end elongated (cerci)

Some of the legs reduced until they basically disappeared

And of course some of the legs remained as walking legs, the six legs that we are all familiar with

The first six segments became thinner and thinner until they eventually fused, becoming the head

The next three segments are the ones the walking legs are attached to, making up the thorax

The rest of the segments comprise the abdomen, absent of any legs

Like so.

And woah! My awful generic drawing turned out looking like the most ancestral insect order we know of, the archeaognatha! How interesting!

You can even make the vestigial remnants of the legs that were on the segments that would later become the abdomen!

So there you have it! Tagmosis is the process of an unspecialized body plan separating into specialized regions, which are called the tagmata. The three tagmata in insects are the head, which specializes in sensory of the environment, the thorax, which specializes in locomotion, and the abdomen, which specializes in digestion and reproduction. From there evolution stretched and squashed segments and legs (and mouthparts) into all different kinds of crazy shapes. The number of segments differs too.

If insects could talk – English preferably! – I would like to ask them what they think is the key to their great success! In particular, I would like to ask a member of each Order of insects, to describe the main innovations and adaptations which have led to the success of their particular group. Since they cannot speak for themselves, I have tried to imagine in this blog what they might say!…

https://www.slideshare.net/Karl_Kjer/karl-kjer-timing-and-pattern-of-insect-evolution

The Tarantula Killers of Texas

An excellent example of behavioral fine tuning during descent with modification (evolution)

Spiders are considered apex predators of the small world inhabited by insects and other small terrestrial arthropods. But, being a spider has its hazards. One of those are the mud daubers, the name from my grandmother that I first knew them by. Some of these predatory wasps are members of Hymenoptera family Pompilidae and go by the common name of spider wasps. These winged marauders hunt down and kill spiders that are often larger than themselves to provide a sufficient cache of food sufficient for one of their larvae over its entire five instar stage development, i.e., one big spider for each descendent. Adult spider wasps feed on plants. Pompilid wasps are atypical among families of insect Order Hymenoptera that evolved eusocial behavior in the Cretaceous Period. (also see Evolutionary Origins of Eusociality in Insects). Rather, they lead a solitary life.

Classification: Class Insecta, Order Hymenoptera, Suborder Apocrita, Superfamily Vespoidea (see note), Family Pompilidae

Note: Ribosomal RNA analysis indicates that Vespoidea is paraphyletic (i.e., members have no common ancestor) and should be resolved into multiple superfamilies.

The 1KITE Project. Trying to resolve the evolution of insects in a large scale.